Technical Field
The present invention relates to a line in which a plurality of machines performs processes in sequence on a workpiece.
Related Art
A plurality of machines (automation devices) is provided in a line which is located in a factory or a workshop, and the plurality of machines performs processes such as fabricating, assembly, and inspection on a workpiece being carried.
Assume here that there is a production line in which a machine a performs a process and a machine b which is located downstream from the machine a in a direction in which a workpiece is carried performs a process immediately after the machine a performs the process. In this production line, the workpiece is carried into the machine a, carried from the machine a to the machine b, and carried out from the machine b automatically by a conveyor. Conventionally, such a production line has employed the following control method. According to the control method, when the production line starts operating, a power source of the machine a and a power source of the machine b are turned on substantially simultaneously so as to cause both the machines a and b to be in a standby state. Then, a start timing at which each of the machines a and b starts performing the process is detected in accordance with an output of a sensor (e.g., a photoelectric sensor or a limit switch) which detects the workpiece being carried. Subsequently, at the start timing thus detected, a state of each of the machines a and b shifts from the standby state to a process performing state (a state in which more electric power is consumed than in the standby state and a process is performed). According to this control method, the machines a and b, whose power sources are always turned on in a period in which the line is in operation, consume, during the standby state, electric power which does not directly contribute to a process such as fabricating or assembly.
Assume also that there is a production line in which, after a machine c performs a process, a machine d which is located downstream from the machine c in a direction in which a workpiece is carried performs a process, and the workpiece is carried from the machine c to the machine d by manpower. In such a production line, it is unnecessary to turn on a power source of the machine c and a power source of the machine d simultaneously. However, in a case where the machine d which is located downstream from the machine c is a heat treatment machine (e.g., a molding machine, a reflow furnace, or a drier), in order to reduce a loss in time for increasing a temperature of the machine d, the machine d may perform idle running (running to maintain an inside of the machine at a standby temperature that is higher than a room temperature) from a start of operation of the line.